Black holes are famous for their immense gravity: they can swallow stars, planets, and even other black holes. But could a black hole consume the entire universe, piece by piece? In short, no. There’s no way a black hole could eat up the universe, or even an entire galaxy, according to NASA. This is why. Black holes are ancient massive stars that have collapsed in on themselves to become incomprehensibly dense, so dense that not even light can escape them. The idea that a black hole could swallow the universe is based on the misconception that they work like vacuum cleaners, sucking space in on themselves, he said. Gaurav Khanna, a black hole physicist at the University of Rhode Island. But that is not the case. “They only swallow things that are extremely close,” Khanna said. In fact, black holes can only devour objects that venture into their event horizon, the point of no return for a black hole, beyond which there is no escape.

For example, the event horizon for a sun-mass black hole would extend only 2 miles (3 kilometers). For an Earth-mass black hole, the event horizon would be only a few inches, about “the size of your thumb,” Khanna said. A black hole’s gravity still impacts the surrounding stars and planets; it can even cause them to orbit, like the black hole at the center of the Milky Way does, but it doesn’t swallow them. York University astronomy professor Paul Delaney gave the following example in an article for the university website: “If our own sun were to (miraculously) transform into a black hole of the same mass, our planet would not it would perceive no change in the gravitational force acting on it and it would continue in the same orbit,” he said. “Of course, it would get very dark and very cold, but the gravity of the black hole at our distance would not be a concern.” It’s also important to note that black holes are quite small, Alexei Filipenko, a black hole expert at the University of California, Berkeley, told Live Science. For a black hole to have a reasonably high probability of swallowing a star, the star in question must point almost directly at the black hole, he said. Over time, this type of cosmic bullseye can occur. But for the sun to be swallowed by the black hole at the center of the Milky Way, for example, it would take a “really enormous amount of time” for the star’s orbit to line up perfectly with the black hole, he said.

Even the largest known black hole in the universe – a cosmic titan called TON 618, weighing an estimated 40 billion solar masses – seems to be close to the theoretical limit of how big black holes can get. This limit comes from the fact that as large black holes gorge themselves on matter, they also release tons of radiation. The radiation heats and ionizes the surrounding matter, making it difficult for gas and dust to cool and fall into the black hole, and ultimately slowing down the rate at which the black hole can feed. This self-regulation prevents black holes from devouring entire galaxies, let alone the entire universe. Then there is the accelerating expansion of the universe to consider. As objects in space get further apart, they are less likely to collide and be captured by a black hole, Khanna said. If a black hole were to devour the entire universe, it would require a monumental change in the direction the cosmos appears to be moving. So you can rest easy, at least when it comes to giant black holes swallowing the universe. They are “nothing we need to worry about,” Khanna said. Unless, of course, the universe is already inside a black hole.